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Pathoma > Pathoma ch. 4 > Flashcards

Pathoma ch. 4 Flashcards

1
Q

Describe the players involved in platelet binding to endothelium and to each other?

A

GP1b receptor binds vWF, which has bound to exposed subendothelial collagen). GP2b/3a receptors bind other platelets via fibrinogen.

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2
Q

Where does vWF come from?

A

Both endothelium (WP bodies) and platelets (a-granules).

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3
Q

What factors are involved in platelet degranulation?

A

ADP is released from platelet dense granules and -> GP2b/3a exposure.TXA2 is produced by platelet COX and promotes platelet aggregation.

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4
Q

2 categories of primary hemostasis disorders?

A

Quantitative and qualitative

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5
Q

What is the main clinical feature of primary hemostasis disorders? Examples?

A

Mucosal and skin bleeding. Epistaxis (most common), hematuria, GI bleeding, hemoptysis, menorrhagia, and intracranial bleeding (with severe throbocytopenia).

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6
Q

Measurements for petechiae, purpura, ecchymoses?

A

1-2 mm, >3 mm, and >1 cm.

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7
Q

What do petechiae indicate about the hemostasis disorder?

A

Thrombocytopenia (not usually seen with qualitative disorders).

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8
Q

Normal platelet count? When do sx show up?

A

150-400 K/uL. <50 = symptomatic.

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9
Q

Normal bleeding time?

A

2-7 min.

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10
Q

What causes prolonged bleeding time? PT/PTT?

A

Platelet disorders. Clotting factor disorders.

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11
Q

MCC of thrombocytopenia is kids/adults?

A

ITP

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12
Q

MOA of ITP

A

IgG against platelet Ags like Gp2b/3a.

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13
Q

When do acute and chronic ITP occur?

A

Acute-following a viral illness/immunization, usually in kids.Chronic-Typical autoimmune presentation in women. Can be primary or secondary (e.g. SLE).

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14
Q

Lab findings in ITP (platelet count, PT/PTT, megakaryocytes)?

A

Thrombocytopenia, normal PT/PTT, increased megas.

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15
Q

Tx for ITP?

A

Corticosteroids (better response in acute, kids).IVIG (distract spleen).Splenectomy (which is producing Ig and eating up platelets).

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16
Q

MOA of microangiopathic hemolytic anemia?

A

Platelet microthrombi in small vessels shears RBCs (hemolytic anemia with shistocytes) and consumes platelets (thrombocytopenia).

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17
Q

When is microangiopathic hemolytic anemia seen?

A

In HUS and TTP.

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18
Q

MOA of TTP?

A

Due to defect in ADAMTS13, which normally cleaves vWF for degradation. The abnormal uncleaved vWF lead to platelet adhesion (thrombotic) and platelet microthrombi(consumption->thrombocytopenia, purpura).

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19
Q

Who usually shows ADAMTS13 defects and what’s the most common defect?

A

Adult females, autoimmune.

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20
Q

MOA of HUS? Cause?

A

Verotoxin from E coli O157:H7causes endothelial damage, leading to microthrombi. (Can also be caused by drugs/infection that damage endothelium).

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21
Q

Who classically gets HUS?

A

Kid who eats undercooked beef

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22
Q

Clinical findings in TTP and HUS? Differences?

A
  1. Hemolytic anemia2. Skin/mucosal bleeding3. Fever4. Renal insufficiency (more in HUS, thrombi in renal vessels).5. CNS abnormalities (more in TTP, “ in CNS vessels).
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23
Q

Lab findings in microangiopathic hemolytic anemia?

A

Same as ITP: thrombocytopenia, increased bleeding time, normal PT/PTT, increased megas on BM biopsy. Also, anemia with shistocytes.

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24
Q

What are the qualitative platelet disorders?

A

Bernard Soulier syndrome, Glanzmann thrombasthenia, use of aspirin, and uremia.

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25
Q

MOA of Bernard Soulier?

A

GPIb deficiency (impaired platelet adhesion).

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26
Q

Lab findings in Bernard Soulier?

A

Mild thrombocytopenia with large platelets (big suckers).

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27
Q

MOA of Glanzmann thrombasthenia?

A

GPIIb/IIIa deficiency (impaired platelet aggregation).

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28
Q

How does aspirin affect platelet fx?

A

Without TXA2, impaired aggregation

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29
Q

How does uremia affect platelet fx?

A

Impairs both adhesion andaggregation.

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30
Q

What’s the purpose of the coagulation cascade?

A

To stabilize the platelet plug by making fibrin (via thrombin).

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31
Q

What are the 3 requirements to activate coag factors?

A
  1. An activating substance2. the phospholipid surface of platelets3. and Ca (from dense granules).
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32
Q

What are the activating substances for the extrinsic and intrinsic pathways?

A

Tissue thromboplastin activates 7 (extrinsic), subendothelial collagen activates 12 (intrinsic).

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33
Q

Clinical features that characterize disorders of secondary hemostasis?

A

Deep tissue bleeding into muscles/joints and rebleeding after a surgical procedure (you were able to form platelet plug but not stabilize it).

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34
Q

What does PT measure?

A

The extrinsic (7) and common (10, 5, 2, fibrinogen) pathways.

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35
Q

What does PTT measure?

A

Intrinsic (12, 11, 9, 8) and common pathways.

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36
Q

Hemophilia A?

A

Factor 8 deficiency (Hemophilia AAAAAight)

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37
Q

Inheritance of hemophilia A?

A

X-linked recessive (remember, more males).

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38
Q

Clinical and lab findings of hemophilia A?

A

Deep tissue and joint bleeds and postsurgical bleeds.Increased PTT, normal PT; Low 8; normal bleeding time.

39
Q

Tx for hemophilia A?

A

Recombinant factor 8.

40
Q

Hemophilia B?

A

Factor 9 deficiency (up 1 letter and #), resembles hemophilia A.

41
Q

MOA of coagulation factor inhibitor dz?

A

Acquired Ab against a coag factor, most commonly 8.

42
Q

Clinical findings in coagulation factor inhibitor dz? What’s the key test?

A

Same as hemophilia A, but won’t correct on mixing study (PTT does correct in hemophilia A).

43
Q

What’s the most common inherited coagulation disorder?

A

von Willebrand dz.

44
Q

von Willebrand dz?

A

vWF deficiency

45
Q

Clinical presentation of von Willebrand dz?

A

Technically, can see features of both primary and secondary hemo disorder bc adhesion is impaired and vWF usually stabilized factor 8, though deep tissue bleeding isn’t usually seen (usually abnormal enough to prolong PTT but not enough to see secondary hemostasis disorder probs).

46
Q

Lab findings in von Willebrand dz? Key test?

A

Increased bleeding time and PTT. Abnormal ristocetin test (ristocetin induces aggregation by causing vWF to bind to GPIb)

47
Q

Tx for von Willebrand dz?

A

Desmopressin increases vWF release from WP bodies.

48
Q

How is vitamin K activated?

A

By epoxide reductase in the liver.

49
Q

Role of vitamin K?

A

Activated, it gamma carboxylates factors 2, 7, 9, 10 and proteins C and S.

50
Q

Who gets vitamin K deficiency?

A

Newborns (lack of colonization, give vit K injection at birth).Prolonged abxMalabsorption

51
Q

How does liver failure affect hemostasis?

A

It produces the coag factors and activates vit K. Monitor with PT.

52
Q

How does a large volume transfusion affect hemostasis?

A

Dilutes coag factors (relative deficiency).

53
Q

Heparin induced thrombocytopenia?

A

Heparin can bind platelet factor 4 (PF-IV) and Abs can then form against this complex, activating these platelets->thrombosis.

54
Q

Disseminated intravascular coagulation?

A

Pathologic activation of coag cascade->1. microthrombi (ischemica/infarction) and 2. thrombocytopenia (bleeding)

55
Q

Conditions that cause DIC?

A

Obstetric complications (TT in amniotic fluid)Sepsis (g -, esp E. coli and N. meningitidis, ->TT production)Adenocarcinoma (mucin activates coagulation)APL (primary granules “)Rattlesnake bite (venom “)

56
Q

Lab findings in DIC? What’s the best screening test?

A

Thrombocytopenia, prolonged PT and PTT, decreased fibrinogen, microangiopathic anemia, elevated D dimer is best.

57
Q

What are d-dimers?

A

Fibrin split products (represent fibrinolysis, which also indicates activation of coag cascade). From fibrin, not fibrinogen!

58
Q

Tx for DIC?

A

Address underlying cause and transfuse blood products and cryoprecipitate.

59
Q

What converts plasminogen to plasmin?

A

tPA

60
Q

What does plasmin do?

A

tPA makes plasmin, which cleaves fibrin (and fibrinogen), destroys coag factors, and blocks platelet aggregation. (lyses clot and does everything it can to also block further clotting).

61
Q

What inactivates plasmin?

A

a2-antiplasmin

62
Q

What characterizes the disorders of fibrinolysis? Examples?

A

Plasmin overactivity. Radical prostatectomy (releases urokinase) and cirrhosis (which makes antiplasmin).

63
Q

What dz can fibrinolysis disorders look like?

A

DIC

64
Q

Lab findings of fibrinolysis disorders? How do you distinguish from DIC?

A

Increased PT, PTT, and bleeding time with normal platelet count; increased fibrinogen split products without elevated d-dimers (fibrinogen is lysed but there aren’t fibrin thrombi to lyse).

65
Q

Tx for fibrinolysis disorders?

A

Aminocaproic acid blocks plasminogen activation.

66
Q

What do lines of Zahn represent?

A

Alternating layers of platelets/fibrin and RBCs (thrombus formation).

67
Q

What distinguishes a thrombus from a post mortem clot?

A
  1. Lines of Zahn2. Attachment to vessel wall
68
Q

Virchow’s triad?

A

Disruption of flow, hypercoagulable state, and endothelial damage.

69
Q

How do endothelial cells prevent thrombosis?

A

Barrier to subendothelial collagen/tissue factor.Produce PGI2 (prostacyclin) and NO.Secrete heparin-like molecules, tPA, and thrombomodulin.

70
Q

What does thrombomodulin do?

A

Redirects thrombin to activate protein C.

71
Q

What do proteins C and S do?

A

Inactivate factors V and VIII, shutting down the cascade (negative feedback).

72
Q

How do B12 and folate deficiency increase risk for thrombosis?

A

By increasing homocysteine levels. (Folate circulates as methyl THF, which transfers its methyl to cobalamin so THF can participate in DNA precursor synthesis. Cobalamin transfers the methyl to homocysteine to make methionine.)

73
Q

What’s the other main cause of elevated homocysteine levels? (this one’s genetic)

A

Cystathionine beta synthase deficiency->homocystenemia with homocystinuria. (CBS convers homocysteine to cystathionine).

74
Q

Homocystinuria?

A

Vessel thrombosis, MR, lens dislocation, and long slender fingers.

75
Q

Classic presentation for hypercoagulable state?

A

Recurrent DVTs or DVTs at young age.

76
Q

Protein C or S deficiency?

A

Hypercoagulable state from this loss of negative feeback (can’t inactivate 5 and 8) on coag cascade.

77
Q

Explain the transient hypercoagulability when warfarin is started?

A

Proteins C and S have a shorter t1/2 than factors 2, 7, 9, 10, so there’s a period where you’ve got the factors but no protein C or S.

78
Q

What is warfarin skin necrosis and when do we worry about it?

A

Warfarin causes a transient imbalance between protein C/S and coag factors. Not much of a problem unless there’s an underlying deficiency of the proteins->thrombosis can occur, esp in the skin.

79
Q

What’s the most common inherited hypercoagulability?

A

Factor V leiden

80
Q

Factor V Leiden?

A

Mutated factor V that lacks the cleavage site that allows proteins C and S to deactivate it.

81
Q

Prothrombin 20210A?

A

An inherited point mutation that leads to overproduction of prothrombin/thrombin.

82
Q

ATIII deficiency?

A

ATIII is responsible for inactivating thrombin and coag factors. Deficiency negates the protective effect of heparin-like molecules being released from the endothelium.

83
Q

Tx for ATIII deficiency?

A

High doses of heparin activate the limited ATIII. Coumadin is then given to maintain the anticoagulated state (can stop heparin after the window in which you’re worried about warfarin skin necrosis).

84
Q

Why are OCPs associated with hypercoagulability?

A

Estrogen induces production of coag factors.

85
Q

Most common type of embolus?

A

Thromboembolus

86
Q

How do you recognize an atherosclerotic embolus?

A

Cholesterol clefts

87
Q

Fat embolus?

A

Associated with long bone fracture, soft tissue trauma. Dyspnea and petechiae on chest.

88
Q

How do you recognize a fat embolus?

A

You’ll see fat, often with bone marrow elements in the pulmonary vessels.

89
Q

When is gas embolus classically seen?

A

Decompression sickness (muscle/joint pain is ‘the bends,’ resp symptoms are ‘the chokes,’ and chronic is Caisson dz). Can be seen in laparoscopic sx.

90
Q

Presentation of amniotic fluid embolus?

A

Dyspnea, neurologic sxs, DIC.

91
Q

How do you recognize an amniotic fluid embolus?

A

You’ll see squamous cells and keratin debris from the fetal skin during labor/delivery.

92
Q

Clinical presentation of PE?

A

Usually clinically silent, but sxs include sudden-onset dyspnea, hemoptysis, pleuritic chest pain, pleural effusion; sudden death from saddle embolus.

93
Q

D dimers high or low with PE?

A

High.

Pathoma (2 decks)

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